Multi-color electrophoretic displays and materials for making the same

Abstract

Novel addressing schemes for controlling electronically addressable displays include a scheme for rear-addressing displays, which allows for in-plane switching of the display material. Other schemes include a rear-addressing scheme which uses a retroreflecting surface to enable greater viewing angle and contrast. Another scheme includes an electrode structure that facilitates manufacture and control of a color display. Another electrode structure facilitates addressing a display using an electrostatic stylus. Methods of using the disclosed electrode structures are also disclosed. Another scheme includes devices combining display materials with silicon transistor addressing structures.

1. A method of driving a multi-color encapsulated electrophoretic display which includes at least one cavity containing at least three species of particles, the particles having substantially non-overlapping electrophoretic mobilities, the display further comprising a first electrode forming a viewing surface of the display and a second electrode on the opposed side of the at least one cavity from the first electrode, the method comprising:
 bringing all three species of particles adjacent one of the first and second electrodes; and 
 applying an electric field between the first and second electrodes to cause at least one species of particles to move away from said one electrode, thereby placing a desired one of the three species of particles adjacent the viewing surface. 
 
     
     
       2. A method according to  claim 1  wherein all three species of particles are first brought adjacent the first electrode, and thereafter application of the electric field causes the two species of particles having the higher electrophoretic mobilities to move away from the first electrode, thereby leaving the species of particles having the lowest electrophoretic mobility adjacent the first electrode. 
     
     
       3. A method according to  claim 1  wherein all three species of particles are first brought adjacent the second electrode, and thereafter application of the electric field causes the species of particles having the highest electrophoretic mobility to approach the first electrode. 
     
     
       4. A method according to  claim 1  wherein all three species of particles are first brought adjacent the second electrode, a first application of the electric field causes the two species of particles having the higher electrophoretic mobilities to be brought adjacent the first electrode, and thereafter the direction of the electric field is reversed, leaving the species of particles having the intermediate electrophoretic mobility to remain adjacent the first electrode. 
     
     
       5. A method according to  claim 1  wherein said at least three species of particles comprise magenta, cyan, and yellow particles. 
     
     
       6. A method according to  claim 1  wherein the at least one cavity has therein a suspending fluid having a density substantially matched to the density of said at least three species of particles. 
     
     
       7. A method according to  claim 6  further comprising an oil-soluble dye in said suspending fluid, said dye being selected from the group consisting of anthraquinone, azo, and triphenylmethane type dyes. 
     
     
       8. A method according to  claim 6  further comprising a surfactant in said suspending fluid. 
     
     
       9. A method according to  claim 8  wherein said surfactant is sodium dodecylsulfate. 
     
     
       10. A method according to  claim 6  wherein the suspending fluid further comprises a charge control agent. 
     
     
       11. A method according to  claim 10  wherein said charge control agent is polyisobutylenesuccinimide, a metal soap or lecithin. 
     
     
       12. A method according to  claim 1  wherein said at least one cavity has therein a suspending fluid which is a halogenated hydrocarbon. 
     
     
       13. A method according to  claim 12  wherein said suspending fluid is tetrachloroethylene. 
     
     
       14. A method according to  claim 12  wherein said suspending fluid is poly(chlorotrifluoroethylene) polymer. 
     
     
       15. A method according to  claim 14  wherein said polymer has a degree of polymerization from about 2 to about 10. 
     
     
       16. A method according to  claim 1  wherein said at least one cavity has therein a suspending fluid which comprises a mixture of two or more fluids. 
     
     
       17. A method according to  claim 1  wherein said at least one cavity is formed in a binder selected from the group consisting of water-soluble polymers, water-dispersed polymers, oil-soluble polymers, thermoset polymers, thermoplastic polymers, uv-cured polymers, radiation-cured polymers, gelatin arabic, gum arabic, polyurethanes, polyamides, urea formaldehyde resin, melamine formaldehyde resin, cellulose, cellulose derivatives, polyvinylacetates, and polyvinylalcohol. 
     
     
       18. A method according to  claim 17  wherein said binder further comprises an additive selected from the group consisting of organic surfactants, organic salts, organic particles, and organic pigments. 
     
     
       19. A method according to  claim 1  wherein at least one of the three species of particles are titania. 
     
     
       20. A method according to  claim 1  wherein at least one of the three species of particles are metal oxide-coated titania. 
     
     
       21. A method according to  claim 20  wherein said metal oxide is selected from the group consisting of aluminum oxide and silicon oxide. 
     
     
       22. A method according to  claim 21  wherein said titania is coated with both aluminum oxide and silicon oxide in either order. 
     
     
       23. A method according to  claim 20  wherein said metal oxide-coated titania comprises two layers of metal oxide coating.